When a patient must be aided in his or her breathing, airways, such as those of a ventilator or anesthesia circuit, are used with equipment, such as a pressure or volume regulated mechanical ventilator circuit, an anesthesia machine, or a humidified enriched gas supply circuit. When a patient is so aided, there often also is the need for placing a sampling adapter in an endotracheal or tracheostomy tube of the patient's airway, so samples of the patient's gas discharge may be taken and monitored with equipment such as a mass spectrometer, a carbon dioxide monitor, respiration or apnea monitor, or other gas analysis equipment.
Currently, commercially available sampling adapters are for example: a steel tube arranged in a right angle embodiment, with a straight portion aligned with the centerline of the airway tube, and a straight portion transversely leaving the centerline to be attached to a sampling gas cannula, which carries the sample of the patient's gas to a respective monitor; and also an adapter which has a sample port or orifice on one side of the adapter to exit a patient's gas to a cannula carrying a gas sample to a respective monitor. Both of these adapters often become clogged with either the patient's sputum, mucus, and/or condensed water. These types of adapters need protection from being blocked by liquids, while being continuously available to deliver the patient's gas samples.
Not for this purpose of keeping a patient's gas sampling line open, but for another purpose of keeping air and gas from mixing with a liquid, which is to be injected into a patient, Phyllis Riely and Robert Skyles in their U.S. Pat. No. 3,631,654 of Jan. 4, 1972, illustrate and describe their gas purge device, which incorporates a disc shaped filter in the fluid flow stream located just before the place where the stream is to be divided into a gas stream and a liquid flow. One portion of the disc is treated to become hydrophobic and another portion of the disc is left untreated and remains hydrophilic. The hydrophobic portion covers the entry to the gas stream, and the hydrophilic covers the entry to the liquid flow, establishing the desired division.
In U.S. Pat. Nos. 4,356,012 and 4,071,040, other uses of hydrophobic membranes are disclosed. Also in U.S. Pat. No. 4,327,718 a drain device is illustrated and described by Richard A. Cronenberg, which continuously removes condensate from an operational patient breathing circuit. A liquid-pervious, gas-impervious material covers a selected opening so condensate can continuously drain through the opening, while the breathing circuit is in operation.
These prior patents, known prior like equipment, and related information, indicate the use of specially treated materials to serve as membranes, baffles, and barriers, to stop gas or to stop liquid, and respectively allow the passage of liquid or gas. Also a special airway adapter was previously designed to withdraw gas from a patient's airway using a porous Teflon filter material, such as the Zitex filter material, which was formed as a large filter disc to cover the tapered entry of a small diameter sampling gas cannula. The filter disc itself was initially protected by a partial conical shield which extended partially into the airway to deflect sputum, mucus, and/or condensed water away from the filter disc located at the margin of the airway. This special airway adapter ws not made available to customers, because the design did not sufficiently overcome sealing problems, dead space problems, emptying problems, signal problems, and new air supply problems. There remained a need for an airway adapter to receive and to direct a liquid free patient's sampling gas to a sampling gas cannula and beyond to equipment monitoring the status of a patient, during relatively long periods of time, without requiring the attention of medical personnel to clean and/or to replace the sampling and testing equipment.